EP0030219B1

EP0030219B1 - A frequency-matched signal device for persons with impaired hearing

Info

Publication number: EP0030219B1
Application number: EP80850181A
Authority: EP
Inventors: Kenth Jack Ajland
Original assignee: Medicinsk Teknisk Konsultation K Ajland AB
Current assignee: Medicinsk Teknisk Konsultation K Ajland AB
Priority date: 1979-11-30
Filing date: 1980-11-28
Publication date: 1984-06-06
Also published as: JPS5694399A; FI803701L; NO147087B; SE7909920L; US4631517A; DE3068136D1; SE419280B; NO803614L; NO147087C; EP0030219A1; DK509880A

Description

The present invention refers generally to a signal device for persons with impaired hearing, by which is meant that the signal device delivers at least two acoustic signals which are located at frequencies to which the ears of the person with impaired hearing are sensitive.
Signal devices for persons with impaired hearing are well-known and include, for example, an electromagnetically operated door-bell (a so-called ding-dong), an optical system connected to door or telephone signals, a tele-loop which by magnetic coupling transmits radio and TV sounds to the hearing aid of the person with impaired hearing. The disadvantage of the electromagnetic bell is that the sound thereof which is amplified and located at quite a low level of frequencies will spread in apartment houses and disturb neighbours who live not only in adjacent apartments but also in apartments at long distances from that of the person with impaired hearing.
The present invention aims at eliminating the disadvantage of the prior electromagnetic bell and instead utiliizing a tone generator which delivers two acoustic signals the frequency of which may be adjusted to those frequencies to which the ears of the person with impaired hearing are most sensitive. These frequencies may be tuned in by the person with impaired hearing himself or the tuning may be made guided by the audiogram (a graph indicating the auditory perception of a person as a function of the frequency) of the person. Owing to the fact that the right and the left ear often do not have identical deficiencies of hearing it is consequently suitable to have the signal device deliver two different tones. Thereby, the sound level of the signal device may be lowered so that adjacent neighbours need no longer suffer from the signal device. The two tones have to be emitted alternatingly by the signal device.
GB-A-1 341 842 relates to an audible alarm device comprising first and second astable multivibrator circuits which in an embodiment of the device can be interconnected. In doing so the device will emit a warbling sound comprising two tones alternating at a "speed" which is set by one of the multivibrator circuits. With the other multivibrator circuit the pitch of one of said tones is set. The pitch of the other tone is related to that of the first-mentioned tone and cannot be varied independently. Therefore this known device cannot be used for the purpose of the present invention.
FR-A-2 21 1 159 relates to a circuit for controlling the two horns of an audio alarm device of the kind used in fire-brigade motorcars. An astable multivibrator and two relays are used to activate the two horns alternately. A monostable multivibrator connected to an alarm switch produces a signal, the duration of which is longer than the period of activation of the alarm switch. During said signal each horn will sound in succession. There are no means by which the pitch of the horns may be adjusted.
In "Elektor", Vol. 5, No. 7/8, July/August 1979 a doorbell drone is described intimating the sound of a bag pipe. The bell automatically cuts out after approximately two seconds irrespective how long time the door bell is pressed, thereby providing an effective remedy against over-enthusiastic bell-pushers. Only one tone is sounding and therefore this device cannot be used for the purpose of the present invention.
Various embodiments of the invention will be described more closely hereinafter with reference to the attached drawings, in which

Figure 1 shows a block diagram of a first embodiment of the device according to the invention;
Figure 2 shows a detailed circuit diagram of the device shown in Figure 1; and
Figure 3 shows a device which is intended to substitute the block of the device according to Figure 1, to permit the production of three or more tones.

In the block diagram of Figure 1, the reference numeral 1 designates a switch which closes at the actuation, for example, of the door- bell, while the reference numeral 2 designates another switch which closes, for example, when the telephone in the apartment of the person with impaired hearing is ringing. When either of the switches closes, a monostable multivibrator 3 is activated at the output of which an output signal is emitted the duration of which is about 5 seconds longer than the period during which the switch is closed. The output signal of the monostable multivibrator is passed to one input of a signal generator 4 in the form of an astable multivibrator at the output of which there is emitted an electrical signal of a certain optionally settable fundamental frequency. The electrical signal is amplified in an amplifier 5 which energizes a loud-speaker 6 which emits an acoustic signal of the fundamental frequency. The frequency depends on the voltage present at a first frequency-sensitive input of the signal generator 4. This frequency is adjustable by means described more in detail hereinafter. A second signal generator, also called a modulator 8, in the form of a second astable multivibrator, has its activating input (not shown) connected to the output of the monostable multivibrator 3 and has its output connected to a second frequency-sensitive input of the first signal generator. When the second signal generator 8 is activated it delivers a voltage at its output which varies between a high and a low level, and the rate of which alternation occurs between these levels is adjustable at circuit elements of the second signal generator described more in detail below. The rate of alternation is slow, for example of the order of about 1/4 Hz. When the second signal generator 8 emits the signal at a low level the signal generator 4 emits an electrical signal at a fundamental frequency and when the second signal generator 8 emits a signal at high level the signal generator 4 emits an electrical signal at its output at a frequency lower than the fundamental frequency. By means of a potentiometer the amplitude of the signal at a high level from the second signal generator may be adjusted. For each amplitude there is a corresponding frequency lower than the fundamental frequency accordingly by varying the amplitude of the signal at high level from the second signal generator 8 the frequency lower than the fundamental frequency may be varied within a range of frequencies which is independent of the set fundamental frequency but dependent on component values included in the circuits. In the preferred embodiment of the invention the signal generator 4 may be adjusted so that the fundamental tone is in the range of about 250 to 2500 Hz while the other signal is freely adjustable, for each setting of the first signal generator 4, within a frequency range extending down to three octaves below the fundamental tone.
To have the acoustic signals of the loud- speaker get a warmer tone it is suitable to control the output signal of the first signal generator 4 at a fixed, low frequency. This is effected by means of a further modulator 9 in the form of a third astable multivibrator which emits a low amplitude signal with a frequency in the order of about 6 to 7 Hz.
So as also to get a blinking optical signal in actuating either of the switches 1, 2 the output of the second signal generator 8 is also connected to a driver amplifier 10 for a lamp 11 which will thus blink concurrently with the tone alternation. A connection 12 to the loud- speaker input may be joined to a tele-loop installed in the apartment of the person with impaired hearing. Possibly, an impedance matching operation must be undertaken before the connection 12 is joined to the tele-loop.
In Figure 2 the detailed circuit diagram of the block diagram shown in Figure 1 is shown. Components in Figures 1 and 2 corresponding to each other have been indicated by the same reference numerals. The monostable multivibrator 3 is built in the conventional way around an operational amplifier. At the closing of either of the switches 1, 2 the multivibrator emits a signal at its output which passes to the non-inverting input of the first astable multivibrator 4 which is also built in the conventional way around a second operational amplifier. The fundamental frequency of the first astable multivibrator 4 is set by means of the potentiometer P1. The electrical signal at the fundamental frequency from the output of the first astable multivibrator is amplified in the amplifier 5 which operates according to the push-pull principle. The amplified signal feeds the loudspeaker 6. The volume may be adjusted by means of a potentiometer P2. The astable multivibrator 4 changes its frequency if the potential difference between its inverting and its noninverting input is changed. According to the invention such a change in the differential voltage is effected by a voltage divider formed by resistors R1 and P3 and connected between the noninverting input of the astable multivibrator 4 and the output of the astable multivibrator 8 which is also built in the conventional way around an operational amplifier. The frequency of the astable multivibrator 8 is adjustable by means of a potentiometer P4. As has been mentioned earlier the frequency of the multivibrator 8 is manifestly slow compared to the frequency of the multivibrator 4. When the slider of potentiometer P3 is at earth the output signal of the multivibrator 4 is only one tone, namely the fundamental tone. In the fully turned-on position of the potentiometer P3 the output signal from the multivibrator 4 varies between two tones concurrently with the fundamental frequency of the multivibrator 8. One tone is the fundamental frequency and the other tone lies about three octaves lower than the former. Thus it is possible optionally to adjust the other tone about 0 to 3 octaves lower than the fundamental frequency set by the potentiometer P1. Said range of frequencies is dependent on the chosen component values of the voltage divider and of the resistors and capac- citors included in the multivibrator 4. The further modulator 9 is likewise composed of an astable multivibrator built in the conventional way which emits a low amplitude signal of the frequency 6 to 7 Hz. This signal passes to the non-inverting input of the operational amplifier in the multivibrator 4.
The output signal of the astable multivibrator 8 also passes to the driver amplifier 10 which includes a Darlington pair T2, T3 controlled by the transistor T1 and connected in the feeder line of the lamp 11. The feed voltage may, for example, consist of a non-stabilized voltage of + 15 volts.
The connection 12 to a possible tele-loop consists of the terminals 12a, b of the loud- speaker 6.
All the four operational amplifiers are included in a single IC circuit of the type pA 324. The other component values are seen from the circuit diagram. The circuit is supplied with a stabilized voltage of + 12 volts which is obtained from a power unit not shown in greater detail. The capacitance values are stated in µF.
The signal device according to the invention can emit more than one tone in addition to the fundamental tone, for example two or more tones in addition to the latter. This may be realized by replacing the second astable multivibrator 8 and the voltage divider R1, P3 in Figure 2 by the circuit shown in Figure 3 which is of a conventional type and therefore is described in a general outline only. The circuit includes a clock pulse generator Cp the clock pulses of which are counted in a modulo-n-counter 13, the counting outputs x, .... x_n of which are connected to a decoder 14 which decodes a desired number of different tones which are obtained at the outputs Z, .... Z_n, the outputs Z,―Zg being shown in the figure. These output signals Z_l-Z₃ are converted in a digital- to-analog converter 15 at the output of which three different sequential voltages are obtained. These voltages are applied to the non-inverting input of the multivibrator 4. Thus, in this case the loudspeaker 6 emits four different sequential tones.

Claims

1. A frequency matched signal device for persons with impaired hearing, including a signal generator (4) provided with a first device (P1) for effecting an optional setting of a fundamental frequency of the signal generator, a modulator (8) which is connected to the signal generator (4) to cause the latter to emit an electrical signal which is alternating at a slot rate between the fundamental frequency and a second frequency, an amplifier (5) connected to the output of the signal generator and a loud- speaker (6) connected to the ampliffier to convert the amplified electrical signal into an acoustic signal alternating between two tones at said slow rate, characterized by a second device (P3, R1) connected between the output of the modulator (8) and the input of the signal generator (4) for effecting an additional setting of the signal generator (4) so that the second frequency is adjustable from the fundamental frequency and downwards, each of said two tones being adapted to the hearing of each respective ear of the person with impaired hearing.

2. A signal device according to claim 1, characterized by the fact that the second frequency is adjustable from the fundamental frequency and about three octaves downwards.

3. A signal device according to claim 2, characterized by the fact that the second device includes a potentiometer (P3).

4. A signal device according to any of the preceding claims, characterized by an astable multivibrator (9) having its output connected to the frequeny-determining input of the signal generator (4) for further modulating its output signal.